Lifting jack



Dec. 2o, 1927.-

C. G. HARRIS LIFTING JACK 2 Sheets-Sheet l Filed Deo. 28. 1925 Y@ @Awma@ 2 Sheets-Sheet 2 vmw C. GQ HARRIS LIFTING JACK Filed Dec. 2B. 1 925 Dec. 20, 1927.

Patented Dec. 20, 1927.r v l y l UNITED sTATEs PAT-ENT oFFics.

' CARLTON G. HARRIS,.0F DENVER, COLORADO, ASSIGNOR OF ONE-THIRD TO J. l.

' BATHBUBN, 0F DENVER, COLORADO.

LIFTING JACK.

- The invention relates to improvements in portable lifting jacks of the general type shown in my atent No. 1,555,842, granted October 6, 1925,.and aas for its object to provide the a paratus ith means for conserving the uid pressure medium, by in suring the return of any of the medium that may leak past the opci'atin pistons to the reservoir; means for provi( ing a slow release of the fluid pressure fromv the power cylinder to the reservoir, when lowering the load, and a quick release thereof, when' the jack is lowered without. load; and means forv preventing excessive. lifting movement of the jack and consequent damageto the apparatus, saidmeans involving mechanism for automatically releasing the fluid pressure, when the lifting element ofthe Jack reaches a predetermined upper limit of inovement. V The invention is lillustrated in the accompanying drawins, in which y Fig. 1 is a sicl elevation of the improved 'ack. l

J Fig. 2 is a partial sectional side elevation of the operating mechanism.

Fig. 3 is-an end elevation. p J Fig. 4' is a fragmentary sectional elevation showing the relation of the main relief valve.

Fig. 5 is asection on the line '5-5 of Fig.

1, with certain 'of the parts omitted to avoid confusion. v

Fig. 6 'is a section on the line 6--6 of Fig. 7 is a sect-ion on `the line 7--7 of Fig.` 5. t j l Referring ft the drawings, it will be observed 'that the general construction. and arrangement of the jack and its operating mechanismgis similar to that shown in my patent aforesaid with the improvements which constitute the instant invention ap-4 plied thereto,but it will be understood that said improvements are not limited to the specific form of jack illustrated and, therefore, the latter is to be regarded as merely exemplary. As indicated more particularly in Fig. 1, 1 indicates the generally rectan lar metal frame, u on which the mechanism is carried, sai frame being provided with forward supporting rollers 2, 2 and a rear swivel; castor 2.v Mounted on the side members of the frame 1 are two A frames or a bell crank lever 5 having a forwardly extending arm 6 and a downwardly extending arm 7, the former supporting a sleeve 10 in which is adjustably mounted a shoe 12 adapted to engage the load, the lower endv of the sleeve 10 bein connected to brackets 3 by reach rods 14 y' means of pins 15`and The lower end of the arm 7 is provided with a .pawl 7 adapted to engage the teeth of an arc-shaped bar 51, which bar is mounted von a shaft journaled in the downward extensions of the bracket 3, said shaft carrying a crank arm 52, to the upper end of which is attached a helical tension s ring 53, which, in turn, is secured to a pu l rod v54 connected to a lever 55 ivoted at '56 to the frame 1, said lever eing engaged by a stop 57, the several parts being constructed and arranged to operate as described in my patent aforesaid. l. y

Secured'between the side members of the frame 1 is a reservoir 25, to the front end of which is attached a c linder 23 in which operates a piston 22 having a forwardly extending connecting rod 21 pivoted to the lower end of arm 7 ofthe bell crank 5. The

forward end of they cylinder 23 is providedv with a ring or annulus 23', which serves as the cylinder 23 is a pump designed to force the fluid ressure medium from the reservoir 25 into tie cylinder 23 behind the piston 22 and thereby effect the proper elevation of the load engaging member of the jack. The pump comprises a barrel 26 in which reciprocates a plunger 28 connected by rod 27 and link 30 to an operating brake or handle 31, `32 pivotally mounted in brackets 33 on the rear'of the frame 1. The forward end of the reservoir 25 is provided with a duct 36, which communicates with the forward end of the pump barrel 26 through the casing of an outwardly openin check .valve 35,

which constitutes the disc arge from thev pump into the cylinder 23, and through ,the casing of an inwardly opening check valve 36', which permits the fluid pressure medium to be drawn by the suction stroke of the pump from the reservoir` 25, as will' be un.

derstood. 1 v

When the pump is operated, the fluid pressure medium is drawn from the reservoir 25 through check valve 3G', duct 36 into the barrel of the pump in front of the plunger 28, as the latter is retracted, and upon the forward movement ofthe plunger, the pressure mediumis forced past kcheck valve 35 into the cylinder 23, thereby forcing piston 22 outward and causing tie power arm 6 of the bell crank 5. to be elevated, the extentvof elevation of the power arm of said bell crank being determined by the number of strokes of the piston 23.

When it is desired to lower the power arm or load engagin end of the bell crank lcver, together with the' load thereon, it is quite necessary that the lowering movement be gradual and steady to avoid damaging the jack or the load supported thereby. On the other hand, when the power arm is to be lowered without a load, it is desirable that the lowering movement be effected quickly, and, to effect these objects, the apparatus is provided with pressure release mechanism interposed between the cylinder 23 and vthe reservoir 25, provided with means to permit a gradual lowering of the load engaging member under load and a ra id lowerin .thereof, when unloaded, sai pressure reease mechanism being constructed and arranged as follows:

Formed in the partition between the reservoir 25 and the cylinder 23 is a valve chamber 40, the outer rim of which is provided with a seat with which cooperates a valve on the end of a rod 71 traversing the reservoir 25 and having its free end projecting beyond the rear wall of the reservoir, and normally engaging a swinging bail 72 pivoted between the side mem ers of the frame 1. The bail 72 is engaged by the end of a lever 73, which is pivoted on a pin 74 secured to the frame 1, s aid lever eing held in its retracted position by a spring 75, which may be conveniently connected at one end to the pivot pin of the pum brake member 31. The outer end of the liever 73 is provided with a pedal 73 adapted to be engaged by the foot of the operator, and also with a lateral detent 79, which is adapted to be engaged by notches and 81 in a latch member 76 pivoted at 77 to a side member of the frame 1, said latch being held normally in position to engage the detent 79 by a spiral spring 78 connected to the lower end of the latch and to the side member of the frame 1. When the detent 79 is engaged in the upper notch 80, the lever 73 is held in retracted relation', so that the valve 70 remains closed, and, when the detent is engaged in notch 81, the lever 73 is locked in its .lower position and valve 70 is held open.

Connected with valve'chamber 40 is a duct 41 having a lateral branch 4l opening into reservoir 25, the outer end of said lateral branch being closed by a suitable screw plug 43, which permits access to the duct. Threaded in the side of the wall of reservoir 25 and in axial alignment with the duct 41 is a screw plug 43, the inner end of which constitutes a throttle valve to regulate the discharge opening between duct sections 41 and 41 and, therefore, to regnlate the rate of discharge of fluid pressure from cylinder 23 into reservoir'- 25, when valve 70 is open. The screw plug 43 is locked in adjusted position by means of a s et nut 43. Also communicating with the valve chamber 40 is a second radial duct 44, which communicates with a lateral duct section 44 opening into reservoir 25 and pro vided with a screw lug 45 in its open end. A screw plug 46 liewise is provided for closing the open end of radial duct 44 and giving access tothe latter for freeing the same of obstructions'. The lateral duct sec-l tion 44 is c'onstricted adjacent the point where it enters. cylinder 25 to provide a valve seat 47 adapted to be engaged by a check valve 47, under certain conditions, thereby to close communication between the cylinder 23 and reservoir25 by way of duct 44, 44', when valve 70 is open, thereby permitting the exhaust of cylinder 23 to be effected past the throttle valve 43 in duct 41' only, so that such exhaust will be relatively slow .and steady. The check valve 47 is normally suspended iii open` relation by means of a stout helical sprinr 48 on the discharge side of said valve, which is held in position by a set screw 48', the opposite side of the valve being acted upon by a relatively weaker spiral spring 49 interposed between the valve 47 and the lug 45. The tensions of the springs 48 an 49 are so adjusted that the check valve 47 is normally held in open positionv and will remain open so long as the discharge of fluid pressure medium from the cylinder 23 into the reservoir is initiated gradually and maintained slowly and substantially uniformly, but will close against the tension of spring 48, if the fluid pressure medium is exhausted violently and rapidly from the c linder 23, as would be the case when va ve 70 is o ened, while the load is supported by the jac r. The closing of the valve 47 by the rush of the fluid pressure medium will immediately check the exhaust of said medium from the cylinder and cause the latter to pass slowlvthrough the constricted opening controlled by the throttle valve 43 in duct 41, so that the load on the jack will be lowered slowly and uniformly without endangering the load or the mechanism of the jack. On the other hand, if it is desired to depress the load 'carrying member of the jack when the latter is not loaded, this may be done manually, by exercising a relatively steady pressure on the shoe 12 or the arm 6 lil) fill

provided with the annulus 23 of the bell crank 5, after the exhaust valve 70 has been opened by depressing lever 73, so that t-he fluid steadily, but without any preliminary surge through valve chamber 40, duct 41, 41 and duct 44, 44", as the check'valve 47 will be held open by spring 48 under such conditions.

`lt has been found desirable to conserve thel fluid pressure medium employed to operate the jack. The ordinary cause of waste is leakage past the piston 22 and in order toA -deliver the recovered leakage, the pump bar.- rel 26 is connected to the reservoir b v'a pipe section 37 provided with an outward y opening-checkl valve 39. Eachforward stroke of the pump plunger 28 will draw in liquid 'from the forward end of cylinder 23 through the ipe 60 into the barrel 26 and the return stro e of the plunger will force the liquid and air drawn into the barrel, into reservoir 25 by way of ipe 37. The excess air will esca e from tie reservoir b ,means of a :f blee er ipe 25', but the liquid constitutin the fini pressure mediumwill be retaine in the reservoir ready for use withthe main body of the fluid pressure medium.

In order to prevent excessive elevation of the load supporting element of the `jack, means are providedD for o erating the exhaust valve 70 as soon as t e load carrying end of the bell crank levei` reaches a predetermined height, said means comprising a rod 90 attached at onel end to the arm 7 of the bell crank lever 5 and the other end of the rod having a sliding connection through an opening in the swin ing bail 72, the extreme end, of the rod being provided with a hook or detent 91, which engages the bail 7 2, v

when the pull rod is moved orward as thel arm 6 of the bell crank 5 reaches its maxi'- mum height, thereby causing the bail to unseat the exhaust valve 70 and permit the fluid pressure in the cylinder 23 to exhaust i sufliciently to lower the load until the abutmenton the'end of pull rod 90 movesV out of engagement with the bail 72. By this means, it is impossible for a careless o erator to elevate the load carrying end o the v'ack' beyond a predetermined limit, as wil be understood.

What `I claim is: 4

1.` A' fluid pressure operated jack, comprising av load engaging member, a power pressure medium exhausts inder, a

. 8 cylinder, l

e piston and load engaging member, a

uid reservoir, a pump interposed betwee a piston therein, a\rod connecting the reservoir and power cylinder having a cylinder and means for returning leakage of the fluid pressure medium through the pump cylinder by action of the pump.

2. .Av fluid (pressure operated jack, c`om. prising a loa engaging member, a power cylinder, a piston therein, a rod connecting the .piston and load/engaging member, a

fluid reservoir, a pump interposed between the reservoir and cylinder, and means for returning leakage of the fluid pressure medium past the piston tothe reservoir, in-

cluding a pi e connecting" the-forward end ofthe` cylin er with .the lrear of the pump barrel,a pipe connectin the pump barrel with the reservoir ande eck valves in said` Pipes y 3. A fluid ressure operated jack, comprising a loa engaging member, a power cylinder, a piston therein, operatively connected with the load engaging member, a

fluid pressure reservoir, a ump having anintake valve connected wit said reservoir and a discharge valve connected to said cylinder, and pressure release mechanism interposed between the cylinder and reservoir provided with a yieldabl held check valve actuatable by flow of flui from the cylinder' to the reservoir to permit a radual lowering of the load engaging mem r under load anda ra id lowering thereof when unloaded.

4. A uid pressure operated jack, comprising a load engaging` member, a `power Idil cylinder, a piston therein, a rod connecting tliepiston and load engaging member, afluid ressure reservoirmounted adjacent said cylpump having an intake valve conf nected with said reservoir' and a discharge valve connected to said cylinder, pressure re- -lease mechanism interposed between the cylinder and reservoir including a main valve, means for operating the same, a duct connecting the main valve chamber with the reservoir, a throttle valve controlling said duct to effect a slow release of pressure from the cylinder, a second duct connecting the main valve chamber with the reservoir, a` check valve interposed in said second duct,

and differential s rings operating on oppoite sides of said c eck valve, whereby a sudden application of pressure on said check valve due to a descending load will close Athe check valve and a gradual application of pressure will not affect said valve, but will permit the rapid release of pressure from the cylinder. a .Y

5. A fluid (pressure operated jack, comprising a loa engaging member, a'power cylinder, a piston therein, a rod. connecting the piston and load engaging member, a fluid reservoir mounted adjacent said `cylinder, a pumppliaving an intake' lvalve conlila',

nected to said reservoir, and a discharge valve connected with said cylinder, and pressure release mechanism interposed between the cylinder and the reservoir and adapted to permit a gradualv lowerin of the load engaging member under loa and a rapid lowering thereof when unloaded, said mechanism including a main valve having a chamber provided with two ducts opening into the reservoir, a throttle Valve controlling one duct, a check valve controlling the other duct, a heavy spring tending to hold said check valve open, and a light spring tending to close the check valve.

6. A fluid ressure opcratedjack, comprisinga loa engaging member, a power cylinder, a piston therein, a rod connecting the piston and load engaging member, a fluid reservoir mounted adjacent said cylinder, a pump having an intake valve connected to said reservoir, and a discharge valve connected with said cylinder, pressure release mechanism interposed between the cylinder and the reservoir adapted to permit a gradual lowering of the load engaging member under load and a rapid lowering thereof when unloaded, said mechanism including a main valve having a chamber provided with two ducts opening into the reservoir, a throttle valve.I controlling one duct, a check valve controlling the other duct, a heavy spring tending to hold said check valve open and a light spring tending to close the check valve, and a pivoted lever for operating the main valve.

7. A fluid pressure operated jack, comprising a load engaging member, a power cylinder, a piston therein, a rod connecting the piston and load engaging member, a fluid reservoir mounted adjacent said cylinder, a pump having an intake valve connected to said reservoir, and a discharge valve connected with said cylinder, pressure release mechanism interposed between the cylinder and the reservoir adapted to permit a gradual lowering of the load engaging member under load and a rapid lowering,r thereof when unloaded, said mechanism including a main valve having a chamber providcd'with two ductslopening into the reser- Voir, a throttle valve controlling one duct, a check valve controlling the other duct, a heavy spring tending to hold said check valve open and a light spring tending to close the check valve, a pivoted lever for operating the main valve, a swinging bail interposed between the lever and the main valve, and a rod connecting said bail and the load engaging member to actuate said bail and open' the main valve when the load engaging member reaches a predetermined elevation.

8. A fluid pressure operated jack, comprising a load en aging member, a horizontal power cylin er, a piston Itherein operatively connected with the load engaging member, a fluid reservoir, a pump interposed between the reservoir and cylinder aving a cylinder, and means for returning leakage of the fluid pressure medium to the reservoir through the pump cylinder.

9. A fluid pressure operated jack, comprising a load engaging member, a horizontal power cylinder, a. piston therein operatively connected with the engaging member, a fluid reservoir, a pump interposed between the reservoir and cylinder, and means for returning leakage of the fluid pressure medium past the piston to the reservoir comprising a tube leading from the cylinder to the pump cylinder having a check valve, and a tube leading from the pump cylinder to the reservoir having a check valve.

l0. 'A fluid pressure operated jack, comprising a load engaging member, a horizontal power cylinder, a piston therein, a

rod connecting the piston and load engaging member, a iluidY reservoir, a pump interposed betweon the reservoir and cylinder, and means for returning leakage of the fluid pressure medium past the piston to the reservoir by action of the pump com rising a tube leading from the ower cylin er in the end thereof opposite t e cylinder intake to the pump cylinder at the end thereof opposite the pump intake having a check valve and a tube leading from the pump cylinder `at said end to the reservoir.

1l. A fluid pressure operated jack, comprising a load engaging member, a power cylinder, a piston therein, operatively con-v nected with the load engaging member, a fluid pressure reservoir, a pump having an intake valve connected with said reservoir, and a discharge valve connected to said cylindcr, and pressure release mechanism interposed between tlie cylinder and reservoir, including a passage between the cylinder and the reservoir, manually controlled means for permitting return of' fluid-therethrough and means controlled by the load on .the load engaging member for regulating the speed of such flow.

In testimony whereof I afiix my signature.

CARLTON e. Hannie. 

